Heretofore, many chemical reagents useful in aqueous and alcoholic media have been unavailable for use in non-hydroxylated media wherein they are normally insoluble. For example, although potassium hydroxide is a commonly employed reagent and benzene a widely used solvent, it has not been possible to dissolve the former in the latter even though finely divided potassium hydroxide is vigorously stirred into boiling benzene. Again, though potassium permanganate is widely used as an oxidizing agent, it has not been possible to employ the same to oxidize, e.g. olefinic compounds in hydrocarbon media because of its insolubility therein. Sodium nitrite, a corrosion inhibitor of iron and steel in aqueous systems, has not heretofore been susceptible to that employment in non-aqueous systems. Thus, a need has existed for a means of carrying normally insoluble reagent substances into solution in non-hydroxylic media.
Cyclic polyethers having four or more oxygen atoms in the polyether ring have been prepared heretofore. A review of the pertinent literature is set out in C. J. Pedersen, J. Am. Chem. Soc. 89, 7017 (1967). In none of the literature reviewed is mention made of formation of stable complexes of the subject cyclic polyethers with salts of ionic metals such as alkali and alkaline earth metals.
According to this invention there are provided macrocyclic polyether compounds. Generally, these compounds can form complexes with the cations of metal compounds, particularly ionic alkali metal and alkaline earth metal compounds. Such complexes are new analytical reagents for use in non-hydroxylated media wherein the uncomplexed metal compounds are normally insoluble.
Macrocyclic polyether compounds of the invention have from 15 to 60 ring atoms in the polyether ring and are compounds of the formula ##STR1## wherein T is C.sub.2 -C.sub.3 alkylene; A is ##STR2## R being H or C.sub.1 -C.sub.18 alkyl, R.sup.2 and R.sup.3 being independently C.sub.1 -C.sub.18 alkyl, C.sub.2 -C.sub.4 alkenyl, or C.sub.6 -C.sub.14 aryl; Q and Z are independently 1,2arylene (or saturated derivatives thereof) or substituted 1,2-arylene (or saturated derivatives thereof), typical substituents being, for example, alkyl, aryl, aralkyl, alkaryl, alkoxy, halo, --CN, carboxy, and carbethoxy, preferred substituents are 1,2-phenylene and 1,2-cyclohexylene; a is 0, 1, 2, or 3; b is an integer from 3 to 20; y is 1or zero; x.sub.7, x.sub.2, x.sub.3, and x.sub.4 are integers independently selected to give a 15-60 atom ring.
Molecular models of representative compounds of the present invention have an annular configuration suggestive of a crown, and accordingly, the macrocyclic polyethers of the present invention are denoted "crown" compounds. Complexes of these compounds with ionic metal compounds are denoted "crown" complexes.
The macrocyclic compounds of the present invention, in the broadest description, are polyether rings having from 15 to 60 atoms in the ring and containing within ring one or more additional groups selected from the group herein before defined by A. The ring carbon atoms can be alkyl-substituted by alkyl groups of about 1-4 carbon atoms. Preferably, alkyl substituents are C.sub.1 -C.sub.2 to reduce stearic hindrance in complexing. The preferred maximum number of ring atoms is 30.
Preferred compounds within the scope of this invention in that they tend to be superior complexing agents are the macrocyclic polyether compounds hereinbefore described wherein T is C.sub.2 alkylene; y = 0; A is ##STR3## and wherein the polyether ring contains about 20 atoms.
Especially good complexing agents are macrocyclic polyether compounds of the following formulas: ##SPC1##
Typical of the crown compounds of this invention are: ##SPC2##
The crown compounds of the present invention are generally made by a sequence of reactions patterned to produce a heterocyclic ring having the desired size and configuration and fused to carbocyclic rings of the proper type and substitution. Undesired side reactions are minimized by employing protective groups to inactivate sites which can compete with the desired ones, by selecting reaction media in accordance with the criteria given below, and by doing any needed hydrogenations before the A groups are present.
In general, an A group can be introduced by reacting a simple reagent having no polyether groups, e.g., CH.sub.2 Cl.sub.2, COCl.sub.2, SOCl.sub.2, R.sup.2 R.sup.3 SnCl.sub.2, R.sup.2 R.sup.3 SiCl.sub.2, HCHO, R'CHO, and (CH.sub.2).sub.3-20 C=O, with hydroxyalkylene groups; thus ##STR4## The diorganometal dichlorides behave analogously. Further, ##STR5## Thionyl chloride reacts similarly. When formaldehyde is employed ##STR6## Aldehydes and the cyclic ketones give acetals and ketals, respectively.
The base used in these preparations varies according to the reaction. The best base for SOCl.sub.2 and COCl.sub.2 is an amine (primary, secondary or tertiary); aqueous base will give lower yields. R.sub.2 R.sub.3 SiCl.sub.2 requires an amine; aqueous bases will not work at all. R.sub.2 SnCl.sub.2 can use amines or aqueous base. The aldehydes and cyclic ketones are reacted in the presence of acids such as p-toluenesulfonic acid, or aqueous alkali (or alkaline earth) metal hydroxides such as KOH; the latter aqueous bases are also suitable for CH.sub.2 Cl.sub.2.
The A group can also be part of a ring bridging element. For example, ##SPC3##
Reactants such as (Cl--CH.sub.2 --CH.sub.2 --0).sub.2 S=0 and (Cl--CH.sub.2 --CH.sub.2 --0).sub.2 C=0 will introduce the respective ##STR7## A groups.
The polyether portion of the crown compound can be built up from reactants having a benzenoid nucleus (or saturated analog thereof) to which a pair of hydroxyl groups are vicinally attached, as in catechol ##SPC4##
or 1,2-cyclohexanediol ##SPC5##
If a crown having a single carbocyclic fused nucleus is desired, a bridging group is built up from one of the vicinal groups and joined to the other vicinal group, or a complete bridging group is attached first to one vicinal group and then to the other. If a crown having two carbocyclic fused nuclei is desired, there are several general methods. In one procedure, a bridging group is attached to (or built up from) one vicinal group on a benzenoid nucleus; then two of these compounds are codimerized, each compound supplying one bridging group which joins the free vicinal group of the other to form the macrocyclic ring. In an alternative procedure, a pair of benzenoid nuclei are bridged; then the ends of a bridging group are attached to the free vicinal groups (one on each nucleus) to form the macrocyclic ring. If a crown having more than two carbocyclic fused nuclei is desired, the needed benzenoid nuclei are bridged in a linear manner to give a polymer having terminal benzoid nuclei bearing one free vicinal group apiece; a bridging group is then attached to these free vicinal groups to form the macrocyclic ring.
When a vicinal dihydroxy aromatic compound such as catechol is employed as the starting point, the crown system of this invention can be formed in a variety of ways making use of the Williamson ether synthesis. A salt of the organic hydroxy compound is reacted with a primary halide EQU G--O.sup.- Metal.sup.+ + Cl--CH.sub.2 --- .fwdarw. G--O--CH.sub.2 --- + Metal.sup.+ Cl.sup.-
General approaches and specific details of crown synthesis are given in J. Am. Chem. Soc. 89, p. 7017 et seq. (1967) and in British Patent 1,149,229.
When a crown compound of this invention is to have a saturated carbocyclic ring, it can be built up from a saturated carbocyclic vicinal diol, such as 1,2-cyclohexanediol, by reacting it with a sulfonate in the presence of a base in a polar aprotic solvent. Preferably tosylates are used EQU G--O.sup.- Metal.sup.+ + Tosyl-OG' .fwdarw. G--O--G' + Metal.sup.+O.sup.--tosyl
Preferred bases are alkali metal hydrides (e.g., LiH), alkali metal hydroxides (e.g., NaOH), or metal tertiary alkoxides (e.g., K tert-butoxide). Typical solvents include diethyl ether, tetrahydrofuran, dimethyl formamide, and dimethyl sulfoxide. Temperatures ranging from room temperature to about the boiling point of the solvent are useful.
It will be evident that classical organic chemical procedures may have to be employed on occasion to protect one or more functional groups present, e.g., one of a pair of vicinal hydroxyl groups. Representative protecting groups for hydroxyl are benzyl, tetrahydropyranyl, methoxymethyl, trityl, and tert-butyl carbobenzoxy. Procedues for protecting functional groups are well summarized in Advances in Organic Chemistry, Vol. III, Interscience Publishers, N.Y., 1963, pages 159-294. British Pat. No. 1,149,229 illustrates the use of protective groups in building polyether crowns; these teachings are applicable here.
At one or more stages in the synthesis of the crown compounds of the present invention a chain-lengthening reaction may be required. The reaction of ethylene oxide with G-OH, an organic compound having a hydroxyl group, gives the following result ##STR8## where n = 1.2, . . . The analogous reaction of oxacyclobutane forms G--O--(CH.sub.2 --CH.sub.2 --CH.sub.2 --O--).sub.n H. The spacing between the oxygen atoms in the heterocyclic ring containing divalent group A can thus be arranged as desired.
The solvents employed for making the crown compounds of this reaction should not interfere with the reaction or adversely affect the crown compound; preferably the solvents should dissolve both the reactants and the product.
When the A group is introduced by an aldehyde, a cyclic ketone, phosgene, thionyl chloride, or a diorganotin dichloride, the solvent (or diluent) can be an aromatic hydrocarbon (such as benzene, toluene, and mixed xylenes), an ether (such as 1,4-dioxane, tetrahydrofuran, a lower alkyl diether derivative of ethylene glycol, such as 1,2-dimethoxyethane, which is preferred, and a lower alkyl diether derivative of a polyethyleneeether glycol having a normal boiling point below 150.degree. C.), and water; alcohols should be absent. When a diorganodihalosilane is employed, water is also excluded from the above list. When methylene chloride and reactants having terminal --CH.sub.2 Cl group are employed, both water and alcohols (e.g., butanol) can be used (as well as the ethers and hydrocarbons mentioned above). The amount of solvent needed can be selected on the basis of operating convenience for a particular set of reactants.
The reactions can be carried out over a wide range of temperatures. For operating convenience, temperatures from about 60.degree. C. to about 140.degree. C. are preferred. The reaction time will vary depending upon the temperature and other factors. Other conditions being equal, the higher the temperature the shorter the time. Typically, time can range from about 6 hours to about 24 hours. The most suitable time and temperature for particular reactants can be determined by routine experimentation.
The crown compound can be isolated by conventional methods such as by concentration of the reaction mixture, chromatographic separation, and mechanical collection of insoluble (or precipitated) product. The crown compounds are chromatographed on acid-washed alumina or silica gel which retains hydroxylated open chain polyethers; the crown is eluted with readily volatile hydrocarbons such as heptane. Identification of the crown compounds is based on elementary C,H,O analysis, molecular weight and nmr spectra. Recrystallization of the purified product can be undertaken to improve its crystalline form. Infrared spectrum can be employed for confirmation.
Carbocyclic nuclei or rings which are vicinally fused to a macrocyclic ring in the crowns are selected from the group consisting of monocyclic and polycyclic aromatic hydrocarbons of the benzo series consisting of from 1 to 3 fused rings (benzene, naphthalene, anthracene, phenanthrene), and the perhydro analogs thereof. The nuclei can be represented as R-substituted, i.e., ##SPC6##
where R is hydrogen, halo, nitro, nitroso, amino, azo, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkenyl, C.sub.6 -C.sub.12 aryl, C.sub.7 -C.sub.16 aralkyl, C.sub.1 -C.sub.4 alkoxy, cyano, hydroxy, carboxy, sulfo and the like and can be attached to any of the available ring positions. Provided the substituent group is stable with the reactants employed in forming the novel crowns of the invention, the group can be present in the vicinally difunctional compounds which are preferred starting materials for the formation of the crown compounds. In other instances the substituent can be introduced after formation of the macrocyclic ring by conventional chemical reaction, e.g., by azo coupling of an amino compound to introduce the azo grouping. In yet other instances, the substituents can be formed by chemical reaction of other substituents, e.g., nitro groups can be reduced to amino groups.
Typical aldehydes useful in making the crowns of the present invention include: formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, n-hexaldehyde, methylethylacetaldehyde, trimethylacetaldehyde, diethylacetaldehyde, cyclopentylaldehyde, n-heptaldehyde, cyclohexylaldehyde, n-octaldehyde, cyclohexylacetaldehyde, nonaldehyde, decanaldehyde, tridecanaldehyde, myristaldehyde, palmitaldehyde, stearaldehyde, benzaldehyde, phenylacetaldehyde, p-tolualdehyde, 1-naphthaldehyde, 2-anthraldehyde, and 2-furaldehyde.
The cyclic ketones useful in making the crowns of the present invention include cyclobutanone, cyclopentanone, acyclohexanone, cycloheptanone, cyclooctanone, cyclononanone, cyclodecanone, cycloundecanone, cyclododecanone, cyclopentadecanone, cyclooctadecanone, and cycloeicosanone.
Typical diorganodichlorosilanes useful in making the crowns of the present invention include:
didodecyldichlorosilane PA1 diethyldichlorosilane PA1 dimethyldichlorosilane PA1 dioctyldichlorosilane PA1 diphenyldichlorosilane PA1 methylvinyldichlorosilane PA1 methylethyldichlorosilane PA1 methyl(propenyl)dichlorosilane PA1 allylmethyldichlorosilane PA1 vinylallyldichlorosilane PA1 ethylpropenyldichlorosilane PA1 cyclopentadienyl(vinyl)dichlorosilane PA1 ethylpentyldichlorosilane PA1 hexylmethyldichlorosilane PA1 ethyl(m-chlorophenyl)dichlorosilane PA1 methyl(p-tolyl)dichlorosilane PA1 ethylphenyldichlorosilane PA1 methyl(sec-octyl)dichlorosilane PA1 dihexyldichlorosilane PA1 dioctadecyldichlorosilane PA1 allylphenyldichlorosilane PA1 cyclopentamethylenedichlorosilane PA1 cyclotetramethylenedichlorosilane PA1 diallyldichlorosilane PA1 methyloctadecyldichlorosilane PA1 phenylmethyldichlorosilane PA1 phenylvinyldichlorosilane
These compounds are described in Organosilicon Compounds, Vol. II, Parts 1 and 2, V. Bazant, V. Chvalovsky, and J. Rathowsky, Academic Press, N.Y., 1965.
Typical diorganotin dichlorides useful in making the crowns of the present invention include: diamyltin dichloride; dibenzyltin dichloride; dibutyltin dichloride; diethyltin dichloride; ethylpropyltin dichloride; diisobutyltin dichloride; diisopropyltin dichloride; dimethyltin dichloride; diisoamyltin dichloride; diphenyltin dichloride; benzylphenyltin dichloride; di-m-tolyltin dichloride; dioctyltin dichloride; di-p-biphenyltin dichloride; dipropyltin dichloride; and divinyltin dichloride. Organotin compounds are described in Handbook of Organometallic Compounds, H. C. Kaufman, D. van Nostrand Co., Inc., 1961.